Overexpression of stearoyl-ACP desaturase enhances accumulations of oleic acid in the green alga Chlamydomonas reinhardtii

FAB2, which encodes stearoyl-acyl carrier protein desaturase, catalyzes the conversion of stearic acid (18:0) to oleic acid (18:1) in fatty acid biosynthesis. In this study, we isolated FAB2 from Chlamydomonas reinhardtii, named CrFAB2, and generated CrFAB2-overexpressing transgenic lines to identify a major role of CrFAB2 in fatty acid biosynthesis of C. reinhardtii. In CrFAB2-overexpressing lines, oleic acid (18:1) content was increased by approximately 2.4-fold compared to the wild-type control plants. Interestingly, CrFAB2 overexpression resulted in the induction of CrFAD2 expression. Consistent with this result, the induction of linoleic acid (18:2) was also detected in CrFAB2-overexpressing lines, and total fatty acid content in these lines was induced by approximately 28 % by CrFAB2 overexpression compared to the wild-type control. Our results indicate that CrFAB2 overexpression enhances the synthesis of oleic acid (18:1) and that CrFAB2 may also play a key role in regulating total fatty acid content in the green alga C. reinhardtii.